Absorbent articles such as sanitary napkins, disposable diapers and incontinence pads are generally made up of an absorbent core sandwiched between a liquid permeable facing sheet and a liquid impermeable backing sheet. The facing sheet contacts the wearer and is either naturally permeable or is apertured to allow discharged bodily fluids to pass through the facing sheet to be thereafter retained in the absorbent core.
With absorbent articles of this nature, it is of particular importance that the facing sheet imparts the impression of dryness, even when the article has been worn for an extended period of time. In addition, the facing sheet must feel comfortable when contacting the skin of the wearer.
Whilst the facing sheet must be permeable to allow fluid to pass through to the absorbent core, the facing sheet should not suffer from rewetting when the absorbent article is subjected to compressive forces which may arise as a result of movement of the wearer. On the other hand, it is important that the apertures in the facing sheet remain open even when the absorbent article is compressed, otherwise discharged fluid will collect on the surface of the facing sheet.
Various facing sheets are documented in patent literature. By way of example, an apertured plastics facing sheet is disclosed in U.S. Pat. No. 4,626,254 in which the apertures are located in depressions arranged in the upper layer of the facing sheet, with the apertures being formed in vertical walls of the depressions. Such a facing sheet is however relatively complicated to manufacture since high precision is required to form the apertures.
A facing sheet is described in EP-A-0 235 309 which comprises non-woven fabric having two layers of different fibre compositions. The layer of the fabric which faces the wearer is apertured. Such a facing sheet is made by forming the first layer by subjecting a fibrous web to a high velocity water jet treatment on a support carrying aperture formation elements, forming the second layer by subjecting a fibrous web to either water treatment or heat fusion treatment, and simultaneously combining the first layer with the second layer by either of these treatments. A disadvantage with such a process is that the process is utilizable on a restricted number of different materials only.
GB-A-2 235 878 describes a facing sheet made up of an apertured hydrophobic resin film and a liquid retentive structure body having a hydrophillic surface and a three-dimensional skeleton structure. The skeleton structure comprises a plurality of randomly distributed pores which communicate with the apertures in the resin film to allegedly allow the rapid introduction of a liquid into an absorbent. The apertures in the resin film may be formed by blow moulding and generally have a diameter lying between 1 and 5 mm. Due to the random distribution of the pores in the skeleton structure, it is difficult to accurately predict the rate of liquid take up of such a facing sheet.
An absorbent article is disclosed in U.S. Pat. No. 4,908,026 having a perforated liquid pervious bodyside liner and a flow zone control layer underlying the perforated region of the bodyside liner. During the perforating process, loose elements of the bodyside liner become entangled with hairy meltblown fibres of the flow zone control layer. It is stated that the loose elements are believed to aid in the transfer of liquid through the flow zone control layer.
U.S. Pat. No. 4,341,217 describes an absorbent article having a perforated outer wrap of liquid impermeable material provided with a multiplicity of protuberances projecting toward an absorbent core. By selecting a particular combination of size and depth of the protuberances, it is asserted that the outer wrap can be made to function both as a topsheet portion and as a backsheet portion.
EP-A-0 214 608 describes an apertured facing sheet comprising a non-woven web network of essentially unbroken thermoplastic fibres. Each aperture is formed by a heated pin which penetrates the nonwoven fabric and separates the fibres thereof, with heat from the pin causing the separated fibres to consolidate and set to prevent subsequent closing of the hole. A disadvantage with such a facing sheet is that the equipment necessary for its manufacture requires very close tolerances since each pin tip has to pass into a corresponding hole with perfect clearance. Again, such apparatus is suitable only for making relatively large diameter apertures.
A further process for forming an apertured plastics facing sheet is to heat a plastic film with hot air as the film passes around an apertured roll. By applying a vacuum within the roll, portions of the plastic film are drawn into the apertures of the roll and burst to thereby create corresponding apertures in the facing sheet. Due however to the application of heat, the properties of the sheet are altered. In addition, the lower periphery of each of the thus burst apertures is uneven and the apertures themselves have a tendency to close when the sheet is subjected in use to compressive forces.